Superlakes, Megafloods, and Abrupt Climate Change

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Science  15 Aug 2003:
Vol. 301, Issue 5635, pp. 922-923
DOI: 10.1126/science.1085921

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About 8200 years ago, the climate of much of the Northern Hemisphere cooled abruptly for a period of about 200 years. In their Perspective, Clarke et al. examine the most likely culprit for this cooling: an outburst of fresh water from a vast, ice-dammed glacial lake in North America. The superlake had formed when the kilometers-thick ice sheet covering much of North America disintegrated. When the ice dam became unstable, fresh water flooded from the lake into the North Atlantic. It remains unclear how this fresh water affected ocean circulation or whether the outburst occurred in more than one stage, but the timing points strongly to the outburst flood as the trigger of the 8200-year climate event.